Rocephin, also known as ceftriaxone, is not a penicillin; it belongs to a class of antibiotics called cephalosporins. While both penicillins and cephalosporins are beta-lactam antibiotics, they have different chemical structures and properties. Therefore, Rocephin can be used in patients who are allergic to penicillin, although caution is still advised due to possible cross-reactivity in some individuals. Always consult a healthcare provider for personalized medical advice.